1. Field of the Invention
The present inventive concept relates to a method and apparatus to measure a step height of a device using a scanning electron microscope (SEM).
2. Description of the Related Art
As semiconductor devices become smaller, the processing margin for forming fine patterns is being reduced. Specifically, the processing margin for the size of pitches of fine patterns as well as the processing margin for etch depths of the fine patterns are being reduced. Therefore, a technology for measuring a 2D critical dimension (CD) to measure a pitch of a fine pattern and a technology for measuring a 3D depth with precision to measure an etch depth of the fine pattern are required.
To measure etch depths of fine patterns, an atomic force microscope (AFM) or optical CD measurement equipment can be used.
The AFM measures an etch depth of a fine pattern using a contact-scanning method that utilizes a probe tip. Therefore, as the number of times that the AFM measures an etch depth of a fine pattern increases, the probe tip of the AFM may wear down, leading to a reduction in measurement reliability.
On the other hand, the OCD measurement equipment theoretically models and calculates light-scattering characteristics of a fine pattern to measure the 3D shape of the fine pattern. The OCD measurement equipment uses a non-contact scanning method. However, the OCD measurement equipment can measure the 3D shape of a fine pattern through calculation only when the fine pattern is uniformly repeated within a spot of light used.